1. Field of the Invention
This invention relates to a resin composite electrolytic copper foil used in producing a printed wiring board, a copper clad laminate having the resin composite electrolytic copper foil and a B-stage resin composition layer laminate molded, a printed wiring board using the copper clad laminate, and a method for producing the printed wiring board. More specifically, it relates to a resin composite electrolytic copper foil having a copper foil with very small unevenness on a copper foil matt surface applied and being excellent in adhesion strength to a resin composition, a copper clad laminate using the resin composite electrolytic copper foil and having good heat resistance, and a high density printed wiring board using the copper clad laminate and capable of forming a fine circuit.
2. Description of the Related Art
In recent years, in order to mount an electronic component such as a semiconductor part for use in an electronic device, a printed wiring board has been demanded to further ultrathin its circuit conductor width and insulating space between circuits, in combination with ultrahigh densification of a semiconductor circuit. Also, a solder upon mounting is, since it is lead free for environmental responsiveness and the mounting temperature becomes high, required to have further heat resistance.
Conventionally, as a copper foil of a copper clad laminate for use in a printed wiring board, an electrolytic copper foil having remarkable unevenness on a copper foil matt surface and good copper foil adhesion strength to a resin has been used. Although these electrolytic copper foils have good adhesion strength, there are problems such that when forming a fine circuit by an etching method, a part of a convex portion of the copper foil is liable to remain on an insulating resin surface due to influence of the unevenness on the copper foil matt surface, that as the etching time is extended in order to completely remove this, the circuit is over-etched, deteriorating location accuracy of the circuit and adhesion strength, and the like. As a means for mending these problems, a so-called low profile copper foil having suppressed unevenness on a copper foil surface has been put to practical use. However, when this copper foil is applied to a copper clad laminate with a highly heat resistant thermosetting resin and the like having essentially weak adhesion strength, lack of adhesion strength becomes a problem in a fine circuit, which has been an obstacle to ultrathinning.
Also from several years ago, in order to improve the adhesion strength between a copper foil and an insulating resin, a method of forming an insulating adhesive layer on a copper foil has come into practical use. For example, in the case of a paper phenol resin copper clad laminate, a method of forming an adhesive layer of phenol butyral resin on a copper foil, in the case of a glass epoxy resin copper clad laminate, a method of forming an epoxy resin adhesive on a copper foil, and the like are known. As specific examples of these resin composite copper foils, a copper clad laminate using a copper foil having a thin adhesive layer formed (e.g. see Japanese Patent Application Laid-open Publication No. H8-216340), a copper clad laminate using a copper foil having a semi-set resin film bonded (e.g. see Japanese Patent Application Laid-open Publication No. H9-011397) and the like have been suggested. However, these resin composite copper foils and copper clad laminates using a copper foil having a semi-set resin film bonded have problems in heat resistance, adhesiveness and heat resistance under moisture absorption, and have required further improvement.
Recently, a surface treated copper foil having particles attached to a surface of a copper foil for improving adhesiveness (see Japanese Patent Application Laid-open Publication No. 2005-248323) has been suggested. However, in a laminate having this surface treated copper foil laminated with an insulating heat resistant thermosetting resin, a fine circuit by an additive method could not be applied to a high density printed wiring board due to the problem of lacking the adhesion, strength of plated copper. Moreover, although a resin composite electrolytic copper foil having a resin composition layer (B) comprising a block copolymerized polyimide resin (a) and 2,2-bis[4-(4-maleimidephenoxy)phenyl]propane (b) formed (Japanese Patent Application Laid-open Publication No. 2008-254352) has been suggested in order to solve this problem, when desmear treatment is conducted in the work process of the additive method, the plate adhesion strength was insufficient. In addition, with the introduction of an environmental responsive lead free solder containing no lead, further high heat resistance is demanded for dealing with a lead free solder process conducted at a temperature higher than before, and improvement has been required.